1. Field
The disclosure relates to integrated circuit (IC) design, and more particularly, to architectures for mixers.
2. Background
Transceivers for wireless communications often incorporate a mixer for up- or down-converting the frequency of a signal. For example, in a communications receiver, a mixer may be coupled to the output of a low-noise amplifier (LNA) to down-convert the output of the LNA by mixing it with a local oscillator (LO) signal.
Various circuit topologies for designing a mixer are well-known in the art. For example, a single-balanced mixer is designed to mix a single-ended input signal with a differential LO signal. One limitation of the single-balanced mixer is that it has relatively poor noise rejection properties compared to other mixer topologies. In comparison, a double-balanced mixer is designed to mix a differential input signal with a differential LO signal. While the double-balanced mixer has relatively good noise rejection properties, it may require the output of the stage preceding the mixer, e.g., an LNA, to be fully differential. A fully differential LNA may consume more power, occupy more die area, and require more IC input pins and/or external matching components than a single-ended LNA. Alternatively, a balun may be provided to transform a single-ended LNA output into a fully differential signal for the double-balanced mixer. However, such a balun may also occupy significant die area, and may introduce insertion loss, which negatively impacts the link budget.
It would be desirable to provide techniques for improving the noise rejection properties of a mixer coupled to a single-ended preceding stage, such as an amplifier.